Advanced Neutron Source Research Articles

Measurement of Isfahan heavy water zero-power reactor kinetic parameters using advanced pulsed neutron source method in a near critical state

The pulsed neutron source (PNS) technique was used to determine the prompt neutron decay constant for two different lattice pitches in the HWZPR heavy water zero power reactor. The results were compared to the variance-to-mean ratio (VTM) method. The neutron mean generation time was also calculated for both pitches, and the results were compared to previous Monte Carlo calculations. The findings of this research can be used as a benchmark nuclear codes to validate kinetic parameters.

Study on A-FNS shielding analysis with variance reduction parameter generation code

Design activities of advanced fusion neutron source A-FNS have been conducted to perform the irradiation tests for fusion reactor materials. It is necessary to evaluate the effective dose rate of the lateral access cell in the A-FNS facility by shielding calculations. In the calculation, a variance reduction method using an effective bias data is necessary to reduce statistical errors. The weight window generation (WWG) function had been used in the analyses with MCNP code and McDeLicious source subroutine. There were some difficulties in the usage of WWG such as many iterative calculations, experiences, and skills required to obtain appropriate bias data. Therefore, the automatic variance reduction parameter generator code ADVANTG has been introduced to the calculation, creating a source description in the general source definition (SDEF) of MCNP for the A-FNS by approximating the neutron and photon generations of the McDeLicious source subroutine. The ADVANTG code was successfully applied to the calculation, and the dose rate of the lateral access cell in the A-FNS was obtained with small statistical errors by a once-through calculation.

Characterization of electroless nickel-phosphorus plating for ultracold-neutron storage

Electroless nickel plating is an established industrial process that provides a robust and relatively low-cost coating suitable for transporting and storing ultracold neutrons (UCN). Using roughness measurements and UCN-storage experiments we characterized UCN guides made from polished aluminum or stainless-steel tubes plated by several vendors.All electroless nickel platings were similarly suited for UCN storage with an average loss probability per wall bounce of 2.8 ⋅ 10-4 to 4.1 ⋅ 10-4 for energies between 90neV and 190neV, or a ratio of imaginary to real Fermi potential η of 1.7 ⋅ 10-4 to 3.3 ⋅ 10-4. Measurements at different elevations indicate that the energy dependence of UCN losses is well described by the imaginary Fermi potential. Some special considerations are required to avoid an increase in surface roughness during the plating process and hence a reduction in UCN transmission. Increased roughness had only a minor impact on storage properties.Based on these findings we chose a vendor to plate the UCN-production vessel that will contain the superfluid-helium converter for the new TRIUMF UltraCold Advanced Neutron (TUCAN) source, achieving acceptable UCN-storage properties with η=3.5(5)⋅10-4.

Conceptual design of the ALIANCE-T mirror experiment

The paper describes the conceptual design of a small-scale experiment within the fusion neutron source project ALIANCE (Axisymmetric LInear Advanced Neutron sourCE). The experimental machine is an axially symmetric magnetic plasma trap with a high mirror ratio, which focuses on the physical and engineering problems of mirror-based gasdynamic neutron sources. The specific research topics covered include the magnetohydrodynamic (MHD) stability of plasmas with high mirror ratios, the operation of the electrodes used for plasma stabilization, and problems related to particle and energy transport. ALIANCE-T features superconducting mirror solenoids that enable it to reach mirror ratios of ∼100 and a helicon plasma source with a power of up to 25 kW installed directly in the confinement zone between the mirrors. The expected plasma parameters are estimated using a simple analytical model, which takes into account gasdynamic axial plasma losses, cross-field transport, and the interaction of the plasma with neutral gas. It is projected that the machine will simultaneously achieve a plasma density >1013 cm−3 and a temperature >10 eV in a continuous discharge lasting for 1–8 h. This paper gives a detailed description of the key machine subsystems and introduces the analytical model used for calculation of the plasma parameters.

Chemical compatibility of F82H and 316L in liquid metal heat transfer mediums Li, Na and NaK

Liquid metals Li, Na and NaK are the candidate heat transfer mediums which are installed in the irradiation capsule of advanced fusion neutron source. The compatibility issue of F82H and 316L in the candidate heat transfer mediums was studied by means of the corrosion tests at the temperature up to 823 K. The depletion of Cr, C and Fe from the steel was caused in liquid Li. The Li diffusion into the steel matrix was analyzed by TOF-SIMS. The corrosion in liquid Na was caused by the Na diffusion into the steel matrix and the surface oxidation. The corrosion in NaK was similar with that in liquid Na.

Prospects for a neutron EDM measurement with an advanced ultracold neutron source at TRIUMF

The TUCAN (TRIUMF Ultra-Cold Advanced Neutron) collaboration is building a new high-intensity ultracold neutron (UCN) source at TRIUMF with the aim of measuring the neutron electric dipole moment (nEDM) with unprecedented precision. TUCAN employs a spallation-driven superthermal UCN production scheme which has been demonstrated with a prototype UCN source. In this article, recent progress on the major components of a new upgraded UCN source and developments in thee context of installation of the nEDM spectrometer are reported.

Conceptual design of advanced fusion neutron source (A-FNS) and irradiation test modules

We have established a conceptual design of Advanced Fusion Neutron Source (A-FNS). In order to obtain irradiation data required in qualifying materials of fusion DEMO DT reactor, we newly designed nine test modules (TMs) to be implemented in the A-FNS. The design of the test modules is based on a new distinctive maintenance scheme: ‘horizontal maintenance method integrated with the shielding plug’. By integrating the TMs with the shield plug and transferring those from the test cell to the access cell, we can avoid disconnecting and connecting the huge amounts of the pipes and cables by means of the remote handling inside the test cell. We determined a configuration of the TMs in the test cell so as to achieve the required irradiation data for each of the test modules. The maximum dpa of F82H specimens in the TM for blanket structural material was about 10 dpa/fpy, which was designed to fulfil critical requirement by accumulated irradiation for two years and operation duration for four years with the operation availability of 50%. A-FNS was designed so that the huge amounts of neutrons generated can be utilized for various non-fusion purposes as well as the fusion materials irradiation. We newly designed a module to produce the significant amount of 99Mo for a medical purpose. The module for such a non-fusion purpose can be installed in the test cell with the compatibility of the fusion materials irradiation tests.

Conceptual design progress of advanced fusion neutron source

Based on the results of the IFMIF/EVEDA project in the broader approach (BA) activities, the conceptual design of the Advanced Fusion Neutron Source (A-FNS) to obtain irradiation data of DEMO blanket materials is under consideration in Japan.This paper describes the progress of the A-FNS conceptual design, which consists of a 40 MeV, 125 mA deuteron beam, a liquid lithium target system, and a test and post-irradiation test facilities. the main objectives of the A-FNS are the acquisition of RAFM irradiation data up to 2035 and the tritium recovery test on the blanket. In addition, it is expected to be used for various neutron researches.The technical design activities of the A-FNS are focused on improvement of the lithium target design, review of impurity criteria, remote handling, and irradiation application plan.

Pulsed Fast Reactor IBR-2 after Modernization

Condensed matter study using nuclear physics methods is one of the main research areas at the Joint Institute for Nuclear Research (JINR), which is stated in the JINR Charter. Since the mid-sixties of the last century, such studies have been successfully carried out at the pulsed reactors/boosters of the JINR. The IBR-2, a powerful high-flux pulsed reactor of periodic operation, was commissioned in 1984 at an average power of 2 MW. In 2007, the reactor reached the service life limit on fuel burn up and fluence on the reactor vessel and was shut down for modernization and replacement of the main equipment. The goal of the modernization was to improve the safety, reliability and experimental possibilities of the reactor for the next 25 yrs of operation. By 2010, the installation of new equipment was completed and followed by a successful physical and power startup. Since 2011, the modernized IBR-2 reactor resumed its operation as a user facility. The IBR-2 reactor with its unique technical approach produces one of the most intense neutron fluxes at the moderator surface among the world’s neutron sources: 1016 n/cm2/s, with a peak power of 1850 MW in pulse. Current status of the reactor, neutron scattering instruments, other experimental facilities and experimental infrastructure will be presented. The designated service lifetime of the IBR-2 will end towards 2030. To keep the experience in the field of condensed matter investigations and to provide a neutron source that complements the steady state PIK reactor, JINR has started activities dedicated to the conceptual design of a new advanced pulsed neutron source at the world level. The parameters of a new source and technical approaches will also be given in the article.

Conceptual design of test modules for DEMO blanket, diagnostic device, and RI production for A-FNS

In the conceptual design activity of advanced fusion neutron source A-FNS, a variety of test modules for fusion DEMO reactor are planned. In these modules, progresses of design activities on Blanket Nuclear Property Test Module (BNPTM) and Diagnostic and Control Device Test Module (DCDTM) were reported. The BNPTM is a module in order to evaluate accuracies of nuclear analyses of the DEMO blanket such as tritium production rate. The influences of the cooling water and test cell wall were evaluated in order to decide its design. The DCDTM is one to achieve irradiation data of functional materials on diagnostic and control devices such as mirror and window. It was clarified from its nuclear analysis that the neutron fluence obtained in the DCDTM was enough to investigate the accumulated irradiation effects on the materials. In addition to the irradiation tests on the fusion reactor materials, various neutron applications are planned at A-FNS. One of the applications is medical isotope production. We clarified that enough amount of the medical isotope molybdenum-99 could be produced in comparison with the demand in Japan by using Radio-Isotope Production Module (RIPM). The RIPM affects little influence on the fusion reactor material irradiation tests.

Optimizing neutron moderators for a spallation-driven ultracold-neutron source at TRIUMF

We report on our efforts to optimize the geometry of neutron moderators and converters for the TRIUMF UltraCold Advanced Neutron (TUCAN) source using MCNP simulations. It will use an existing spallation neutron source driven by a 19.3kW proton beam delivered by TRIUMF’s 520MeV cyclotron. Spallation neutrons will be moderated in heavy water at room temperature and in liquid deuterium at 20K, and then superthermally converted to ultracold neutrons in superfluid, isotopically purified 4He. The helium will be cooled by a 3He fridge through a 3He–4He heat exchanger.The optimization took into account a range of engineering and safety requirements and guided the detailed design of the source. The predicted ultracold-neutron density delivered to a typical experiment is maximized for a production volume of 27L, achieving a production rate of 1.4 ⋅ 107s−1 to 1.6 ⋅ 107s−1 with a heat load of 8.1W. At that heat load, the fridge can cool the superfluid helium to 1.1K, resulting in a storage lifetime for ultracold neutrons in the source of about 30s. The most critical performance parameters are the choice of cold moderator and the volume, thickness, and material of the vessel containing the superfluid helium.The source is scheduled to be installed in 2021 and will enable the TUCAN collaboration to measure the electric dipole moment of the neutron with a sensitivity of 10−27ecm.

Applicability of alleviated limits of non-metallic impurities in lithium for advanced fusion neutron source

The alleviated limits of impurities of nitrogen and hydrogen isotopes in lithium are suggested to be 400wppm and 550appm, respectively for early realization of Advanced Fusion Neutron Source planned in Japan. The applicability of the suggestion is discussed by comparing to that of IFMIF. As the results, not less than 4-year buffer for R&D of nitrogen trap are brought in, which is thought as one of bottle neck. Additionally, the application of this suggestion would diminish the beryllium (a radioactive isotope will generate in A-FNS process) concentration in processing lithium, as well. On the other hand, it is indicated that there would be no fatal problems by application of the present suggestion.

Deflection predictions of involute-shaped fuel plates using a fully-coupled numerical approach

This paper describes the modeling and simulation of fluid structure interactions (FSI) of involute-shaped fuel plates used in nuclear research reactors. We believe this to be the first time that this type of application is described in the literature using a fully-coupled, and monolithic, finite element approach. The simulations are validated against plate deflection data for the conceptual design of the Advanced Neutron Source Reactor (ANSR), which was envisioned to be the world’s most powerful nuclear research reactor for neutron scattering and other applications, but was ultimately never completed. The high performance of the ANSR creates a bounding envelope for involute-shaped research reactors such as that used in the High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) which is undergoing research for the conversion from highly-enriched uranium (HEU) to low-enriched uranium (LEU) fuel. As such, the findings from the present FSI analyses carried out herein for the ANSR plates provide good guidelines and inform designers what should be expected for the next generation of plates in the HFIR. It is shown herein that the current approach can accurately capture the leading-edge deflections of the involute-shaped plates and simulations can predict the ‘S-shaped’ deflection of the first mode instilling confidence in the methodology.

Searches for Electric Dipole Moments—Overview of Status and New Experimental Efforts

Searches for permanent electric dipole moments (EDMs) of fundamental particles, atoms and molecules are promising experiments to constrain and potentially reveal beyond Standard Model (SM) physics. A non-zero EDM is a direct manifestation of time-reversal (T) violation, and, equivalently, violation of the combined operation of charge-conjugation (C) and parity inversion (P). Identifying new sources of CP violation can help to solve fundamental puzzles of the SM, e.g., the observed baryon-asymmetry in the Universe. Theoretical predictions for magnitudes of EDMs in the SM are many orders of magnitude below current experimental limits. However, many theories beyond the SM require larger EDMs. Experimental results, especially when combined in a global analysis, impose strong constraints on CP violating model parameters. Including an overview of EDM searches, I will focus on the future neutron EDM experiment at TRIUMF (Vancouver). For this effort, the TUCAN (TRIUMF Ultra Cold Advanced Neutron source) collaboration is aiming to build a strong, world leading source of ultra cold neutrons (UCN) based on a unique combination of a spallation target and a superfluid helium UCN converter. Another focus will be the search for an EDM of the diamagnetic atom 129 Xe using a 3 He comagnetometer and SQUID detection. The HeXeEDM collaboration has taken EDM data in 2017 and 2018 in the magnetically shielded room (BMSR-2) at PTB Berlin.

Investigation of Mo-99 radioisotope production by d-Li neutron source

A plan of an advanced fusion neutron source (A-FNS) by using d-Li reaction is in progress at Rokkasho in Japan. We investigate multipurpose usages of the A-FNS in addition to fusion material irradiation test. Production of medical isotope 99Mo is considered as one of the usages. We conducted a conceptual study on a module for radioisotope production which was composed of a neutron spectrum shifter and a neutron reflector. We examined impacts of materials of the shifter and reflector on amounts of the 99Mo production, and their thicknesses. It was concluded that beryllium is the most suitable material both for the shifter and the reflector from the viewpoint of the 99Mo production. It was shown that we produced an enough amount of the 99Mo for the demand in Japan. We can apply natural molybdenum for this purpose. It was also shown that we could use a part of irradiation capsules in high flux test module, which was for the fusion material irradiation test originally, by using isotopically enriched 100Mo to meet that.

The time-of-flight Small-Angle Neutron Spectrometer at China Spallation Neutron Source

The vision for an advanced accelerator-driven neutron source in China started in the late 1990s, followed by the China Spallation Neutron Source (CSNS) breaking ground in Dongguang in 2011 and obta...

7 Advanced Neutron Source Project

7 Advanced Neutron Source Project

Neutronics and Safety Studies on a Research Reactor Concept for an Advanced Neutron Source

This paper presents preliminary neutronics and thermal hydraulics safety analysis results for a low-enriched uranium (LEU) fueled research reactor concept being studied at the National Institute of Standards and Technology (NIST). The main goal of this research reactor is to provide advanced sources for neutron scattering experiments with a particular emphasis given to high intensity cold neutron sources (CNSs). A tank-in-pool type reactor with an innovative horizontally split compact core was developed in order to maximize the yield of the thermal flux trap in the reflector area. The reactor concept considered a 20 MW thermal power and a 30-day operating cycle. For non-proliferation purposes, a LEU fuel (U3Si2-Al) with 19.75 wt% enrichment was used. The core performance characteristics of an equilibrium cycle with several representative burnup states—including startup and end of cycle—were obtained using the Monte Carlo–based code MCNP6. The estimated maximum perturbed thermal flux of the core is ~5.0 × 1014 n/cm2-s. The calculated brightness of the CNS demonstrates an average gain factor of ~4 compared to the current source operated at the existing NIST reactor. Sufficient reactivity control worth and shutdown margins were provided by hafnium control elements. Reactivity coefficients were evaluated to ensure negative feedback. Thermal hydraulics safety studies of the reactor were performed using the multi-channel safety analysis code PARET. Steady-state analysis shows that the peak cladding temperature and minimum critical heat flux ratio are less than design limits with sufficient safety margins. Detailed transient analyses for a couple of hypothetical design-basis accidents show that no fuel damage or cladding failure would occur with the protection of reactor scrams. All these study results suggest this new research reactor concept offers a demonstrable potential to greatly expand the cold neutron capability with a 20 MW power and certified LEU fuels.

Validation of liquid lithium target stability for an intense neutron source

This paper reports on validation results for the stability of a liquid lithium (Li) target intended for use as an intense fusion neutron source such as for the International Fusion Materials Irradiation Facility (IFMIF), an advanced fusion neutron source (A-FNS), and a demonstration fusion power plant (DEMO)-oriented neutron source (DONES). The variation in the thickness of a Li target must be suppressed to within ±1 mm inside a deuteron beam footprint to both maintain the integrity of the Li target and guarantee the desired level of neutron flux. We achieved a stable Li target with an average thickness variation of just 0.17 mm inside the beam footprint under standard IFMIF operating conditions (target speed: 15 m s−1; vacuum pressure: 10−3 Pa; and Li temperature: 250 °C). Moreover, the mean and maximum wave amplitudes at the beam center under such conditions were found to be 0.26 mm and 1.46 mm, respectively; these are small enough to satisfy operational requirements. Finally, it was determined that the stability of the Li target remained unchanged despite using it for an extended period of 1561 h. This finding is regarded as a significant step toward the realization of the IFMIF and the potential use of relevant neutron sources such as A-FNS and DONES.

ICANS XXI, Mito, September 29–October 3, 2014

The 21st International Collaboration on Advanced Neutron Source (ICANS) meeting took place at Mito, Japan (September 29–October 3, 2014). It was organized and hosted by Japan Proton Accelerator Com...